CDMA trunked communication system combines the CDMA techniques with the dedicated dispatch communication system, and by using the half-duplex communication method, it can realize fast connection, and support group call (namely, a one-to-multiple calling method), therefore it can be widely applied in enterprises, security department, police department and military that require for a high demand of command and control functions.
The standard group call service (also named as traditional group call service or broadcast group call service) in CDMA trunked communication system supports group call for the group with large capacity (a group comprises thousands of users and they all locate within a small sector) within a small scope through the method of sharing the forward and reverse service channels in the sectors.
In the standard group call service in CDMA trunked communication system, each terminal in the group can have different status at different times: speaking status and listening status. When a terminal is in the speaking status, it is called the speaking terminal and when the terminal is in the listening status, it is called the listening terminal or non-speaking terminal. Since the standard group call service employs half-duplex communication method, there can be at most only one speaking terminal in one group at a time and others are all listening terminals. The speaking terminal can send out voice and signaling in the reverse link while the listening terminal can only send signaling but no voice in the reverse link.
In order to support the needs of standard group call service in CDMA trunked communication system, the reverse traffic channel built in each sector on the Base Station (BS) side in dispatch area comprises: one reverse dedicated traffic channel and one or more reverse shared traffic channels. The reverse dedicated traffic channel is used to transmit reverse voice and signaling by the speaking terminal that may exist in the sector; the reverse shared traffic channel is used to send reverse signaling by all the listening terminals of said group in the sector.
In the standard group call service, since the terminal can only be in one status at any moment, and while in listening status and speaking status, the reverse traffic channels for transmitting reverse information are different, it needs to solve the fast switching problem of the reverse traffic channels when the two different statuses of the terminals are switched.
The current on-going CDMA group call service allocates one dedicated reverse traffic channel for each terminal in the group. Although the terminal can be in different status at different times, however, there is no problem about switching between the dedicated reverse traffic channel and the shared traffic channel. As a result, the current on-going CDMA group call service does not provide a technical solution for realizing fast switching of the reverse traffic channels when the two different statuses of the terminals are switched.